JP2009122099A - Method and device for repairing core spray downcomer in nuclear reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slip joint assembly (32) for a downcomer (10) of a core spray system in a reactor pressure vessel (12). <P>SOLUTION: The slip joint assembly (32) includes housing sleeves (40 and 42), formed around a slip joint (22) of a downcomer, with an annular cavity present between the inside surface of the housing sleeves (40 and 42) and the downcomer; an upper wedge (46) and a lower wedge (46) which can be inserted into the cavity; a wedge bolt (60) extending through the cavity and the upper and lower wedges (46) and exerting the force for pulling the upper and lower wedges (46), to fit them with each other so as to fix the housing sleeves (40 and 42) onto the downcomer; and an upper pin (36), extending from the housing sleeves (40 and 42) into an opening (34) in the upper section of the downcomer and a lower pin (36) extending from the housing sleeves (40 and 42) into an opening (34) in the lower section of the downcomer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates generally to nuclear reactors, and more particularly to an apparatus and method for repairing or replacing welds in piping within a nuclear reactor pressure vessel.

  A boiling water reactor (BWR) reactor pressure vessel (RPV) is typically generally cylindrical and is closed at both ends, for example, by a lower head and a removable upper head. A core shroud usually surrounds the reactor core and is contained within the RPV.

  Boiling water reactors generally have piping for core spray cooling water. The core spray piping is used to send water from outside the RPV to the core spray sparger in the RPV. The core sprayed pipe generally includes a vertical downcomer. The upper and lower sections of each downcomer are typically joined during reactor assembly. The upper piping section is adjusted to provide the appropriate length and fit with the lower pipe section. Slip couplings welded to the upper and lower tube sections prevent cooling water leakage and provide the structural strength required by the downcomer piping system.

  The BWR core spray piping system in operation has a welded structure. The welded portion of the thermal sprayed piping is susceptible to stress corrosion cracking, especially intergranular stress corrosion cracking (IGSCC). Reactor components are subject to various stresses related to other stress sources such as differential thermal expansion, working pressure required to contain reactor cooling water, and residual stresses in welding, cold work and other heterogeneous metal treatments. Receive. Water chemistry, welding, heat treatment, and radiation can increase the likelihood of stress corrosion cracking of metals in parts. Accordingly, the need for devices and methods for repairing downcomer welds has long been recognized.

  Repair or strengthening clamping devices have been developed that provide structural support for downcomer welded joints. Reinforcing slip joint clamps were developed to structurally replace the slip joint between the upper and lower sections of the downcomer. The slip joint clamp fits over the welds and sleeves previously attached to join the upper and lower sections of the downcomer and functions as a support sleeve. The slip joint clamp may include a clamp assembly (sleeve) consisting of a plurality of parts that are fitted over the welded slip joint. A slip joint assembly was developed for the downcomer of the reactor pressure vessel core spray system, which is a slip joint assembly in the downcomer in the downcomer where an annular cavity exists between the inner surface of the housing sleeve and the downcomer. Enclosed housing sleeve, upper and lower wedges that can be inserted into the cavity, extend through the cavity, and extend through the upper and lower wedges and descend the housing sleeve A wedge bolt that applies a force to pull the upper and lower wedges together to secure the tube, an upper pin extending from the housing sleeve into the opening in the upper section of the downcomer, and a lower section of the lower tube from the housing sleeve And a lower pin extending into the opening.

  A method of assembling a slip joint clamp assembly for repairing the downcomer of a reactor pressure vessel core spray system has been developed, using a guide wire and a step of placing a housing sleeve around the slip joint Position the lower wedge and the wedge bolt that extends through the lower wedge and into the container so that the lower wedge is under the housing sleeve around the slip joint and the bolt is in the space between the sleeve and the downcomer A step of lifting the lower and wedge bolts with a guide wire so that the lower wedge moves into the cavity and the upper end of the wedge bolt extends over the housing sleeve, and the upper wedge descends the guide wire Step to slide to the wedge bolt, and secure the nut to the top and top of the wedge bolt And attaching on top of rust, tighten the nut on the wedge bolt comprises whereby the step of applying a force to attract the upper wedge and lower wedge together. The guide wire is then removed from the wedge bolt and removed from the reactor vessel.

  A slip joint clamp assembly has been developed that attaches to the downcomer and secures the welded slip joint in the tube. The slip joint clamp assembly structurally replaces or strengthens the existing slip joint welding sleeve that joins the upper and lower sections of the downcomer.

  1 shows a downcomer 10 of a core spray cooling water system of a boiling water reactor (BWR) 12 having a reactor pressure vessel (RPV) outer wall 14 and a reactor shroud 16. The downcomers 10 each descend vertically and extend into an annular cavity between the outer wall 14 and the shroud 16 and connect to an elbow 18 that connects to a conduit 20 that extends through the wall of the shroud 16. . Cooling water from the downcomer flows through the elbow pipe and pipe to the sparger pipe inside the shroud and over the reactor core. The core spray sparger piping inside the shroud and the associated spray nozzle are conventional and are not shown in FIG.

  FIG. 2 is a schematic cross-sectional view of the slip joint 22 between the upper and lower tube sections 24, 26 of the downcomer. A slip joint 22 connects the upper section 24 and the lower section 26 of the downcomer. The lower tube section 26 can be of various lengths depending on the height of the core spray piping line passing through the shroud. A slip joint 22 joins the opposing ends of the upper and lower tube sections 24, 26 of the downcomer. The joint may include a cylindrical sleeve 28 around the ends of the upper and lower sections of the tube and an annular receptacle 30 that supports the sleeve. The receptacle is welded to the lower downcomer section 26, the sleeve is welded to the upper downcomer section, and the sleeve and receptacle are welded together.

  FIG. 3 is a side perspective view of two downcomers 10 coupled to the walls of the reactor core shroud 16 via elbow 18 and conduit 20, respectively. To better show the downcomer, the RPV wall is not shown in FIG. The downcomer on the left side of FIG. 3 is ready for slip joint clamp placement. The slip joint clamp 32 is shown installed on the right downcomer.

  The slip joint clamp, in one embodiment, is a cylindrical sleeve that fits over the slip joint 22 (see sleeve 28 and annular receptacle 30) and joins the upper section 24 and lower section 26 of the downcomer. The slip joint is made or assembled during RPV assembly, but the slip joint clamp 32 is installed after the RPV is assembled and the reactor core is in operation. The slip joint clamp assembly may be installed as a repair component in advance for the failed slip joint. The slip joint clamp 32 may be installed while the reactor is shut down and the RPV is open for inspection. Machining the conical hole 34 above and below the slip joint is the initial step in installing the slip joint clamp 32. The conical hole can be machined by electrical discharge machining (EDM), which is performed by lowering the EDM actuator to the desired hole position on the upper and lower sections 24,26 of the downcomer. A pair of conical holes 34 is formed on each side of each of the upper and lower sections of the downcomer. The conical hole 34 receives four lateral pins 36 that secure the slip joint clamp to the downcomer. The transverse pins each have a conical tip 37 (FIG. 5) seated in a corresponding downcomer conical hole 34.

  FIG. 4 is a perspective view of the slip joint clamp 32 shown fully assembled but separated from the downcomer. In practice, the slip joint clamp is assembled around the downcomer. The slip joint clamp includes a pair of opposing half-housings 38, 42 that fit together to form the sleeve of the downcomer. The half housing includes a male half housing 38 having a male connector 40 (eg, a dovetail) extending along the axial edge of the half housing. The female half-housing 42 is attached to the male half-housing by, for example, a mating dovetail groove 44 that receives the male connector 40. Preferably, the female half housing slides axially over the male connector so that the female half housing is attached to the male half housing by lowering the female half housing onto the male half housing. Each half-housing may form a half of the cylindrical sleeve of the slip joint clamp and may be semicircular in cross section.

  When assembled, the male and female half housings 38, 42 form a cylindrical sleeve around the downcomer. A void remains between the inner surface of the half housing and the downcomer. The void is sufficient to allow the slip joint clamp to slide over the slip joint. When the slip joint clamp 32 is secured to the downcomer, the lateral pin 36 and the wedge 46 ensure that the upper and lower sections of the tube remain joined even if the slip joint weld deteriorates. A transverse pin 36 and associated conical hole 34 in the downcomer piping section establishes the relative position of the slip joint clamp assembly relative to the downcomer slip joint. The wedge 46 maintains a uniform annular space between the slip joint clamp assembly and the downcomer piping. A wedge 46 is disposed between the inner surface of the assembled half-housings 38, 42 and the downcomer.

  FIG. 5 is a cross-sectional view of the slip joint clamp attached to the downcomer. FIG. 5 shows the engagement of the lateral pin 36 to the slip clamp assembly 32 and the upper downcomer 24. A threaded lateral pin 36 engages a right-handed opening 66 in one half housing 42 of the slip clamp assembly. Each pin 36 has a conical tip 37 seated in a corresponding one of the conical holes 34 of the downcomer 24. The crimp collar 62 has a left-hand thread on the outside and seats in a half-chassis right-handed opening 66 and a coaxial threaded recess 63 (the left-hand thread is actually in the opening 66 drilled against it). . In order to prevent the pins from rotating off during operation of the reactor vessel, the crimp collar is deformed into a machined groove in the cylindrical head 39 of the transverse pin 36.

  FIG. 6 is a side view of an exemplary wedge 46. The wedge may be a generally rectangular mass of stainless steel with a relatively wide end 48, a narrow end 50, and an inclined sidewall 52 between the ends. The inclined side wall may be a flat surface adapted to fit and slide into a groove 54 (see FIG. 4) on one internal surface of the half-housings 38,42. The opposing side walls 56 of the wedge 46 may be curved in cross section to abut the outer surface of the downcomer. The wedge includes a bolt slot (hole) 58 that extends axially through the wedge and is adapted to receive the axis of the wedge bolt 60 (FIG. 4). Bolt 60 extends through upper and lower wedges 46 disposed in the upper and lower sections of slip clamp assembly 32. Each bolt extends (axially) through the slip clamp assembly and applies an axial preload (tensile force) to the wedges 46 at opposite ends of the bolt. The axial preload of the bolt causes the wedge to slide inward along the sloping surface of the housing groove 54. As the wedges are drawn together, they surround the downcomer and the slip joint in the slip joint clamp housing, thereby supporting the downcomer.

  FIG. 7 is a perspective view of the half housing 42 (specifically, a female half housing). The inner surface 64 of the half housing faces the outer surface of the downcomer when the housing is installed on the tube. The inner surface of the female half housing 64 is substantially the same as the inner surface of the male half housing. The inner surface 64 of each half housing includes a cylindrical surface that is generally smoothed around the downcomer. A threaded hole 66 along the axial centerline of the half housing is provided for the crimp collar and lateral pin 36. The inner surface includes a groove 54 having a sloped surface that receives the sloped sidewalls of the wedge.

  The groove 54 is disposed in the upper and lower end portions 70 of the half housing. Further, each groove is axially aligned with the other groove at the opposite end of the half housing. In one embodiment, 8 pairs (grooves) are symmetrically arranged around the inner surface of the half-housing. Preferably, the groove 54 is deepest at the axial end 70 of the half-housing and becomes progressively shallower as the groove goes axially inward along the inner surface 64 of the half-housing. Each groove 54 may have an inner end 72 in the axially inner section of the inner surface of the half housing. A narrower slot 74 provides a gap for a wedge bolt that extends between a pair of axially aligned grooves 54.

  8 and 9 are perspective views of the slip joint clamp 32 assembled around the downcomer 10. As shown in FIG. 8, the connector 40 of the male half housing 32 has finished sliding in the axial direction and is within the slot 44 of the female half housing. Further, the transverse pin 36 is shown inserted and engaged with a conical hole 34 provided in the downcomer to receive the pin.

  In addition, a guide wire 76 (eg, a flexible stainless steel cable) supports the end of each wedge bolt 60 during the assembly process. The guide wire 76 may extend from the fuel exchange floor of the reactor core containment building to the slip joint of the downcomer. The lower wedge 46 slides over the wedge bolt and a guide wire is attached to the upper end of the wedge bolt. The wedge, wedge bolt and guide wire are preferably connected to one half housing when the assembled half housing is assembled around the downcomer and slides over the slip joint into place. Configured to pass through a slot on the inner surface (item 74 in FIG. 7) (inserted after housing assembly and lateral pin insertion). In the embodiment disclosed herein, four assemblies of guide wires, wedge bolts, and lower wedges are disposed in respective slots 74 of the mating half housing.

  The guide wire 76 assists in aligning the lower wedge 46 and the wedge bolt 60 with respect to the respective groove 54 and slot 74 of the half housing. The guide wire may extend to the core refueling floor, where the wire is controlled by a technician installing the slip joint clamp. The guide wire may also use the guide wire to move the assembly axially along the tube to assist in positioning the slip joint assembly on the slip joint.

  As shown in FIG. 9, the wedge 46 is positioned below the lower axial end of the half housing until the housing is aligned with the slip joint and the lateral pin 36 is turned into the hole 34 in the downcomer. The As shown in FIG. 9, the guide wire lifts the wedge bolt and lower wedge so that the lower wedge slides into the individual grooves 54 in the lower portion of the half-housing. In addition, the guide wire 76 pulls the wedge bolt through the space between the slip joint clamp and the downcomer and fits into a slot 74 on the inner surface of the half housing.

  The upper wedge 46 is lowered along the guide wire 76 to the wedge bolt 60. The upper wedge slides over the upper end of the bolt and slides into the respective groove 54 at the upper axial end of the half housing.

  FIG. 10 is a perspective view of the upper section of the slip joint clamp 32 with the upper wedge 46 sliding into the groove 54 of the half housings 38, 42. The upper threaded end of the wedge bolt 60 extends upward through the wedge. A predetermined torque is applied to the locking nut 80 to provide the desired tension on the bolt and the opposing pair of wedges 46 on the bolt. The pulling force causes the wedge to slide into the sloping groove 54 and firmly abut both the half housing and the downcomer. The slip joint clamp assembly is secured to the downcomer by a wedge and a lateral pin.

  The upper end of the bolt is attached to the guide wire 76 by a stainless steel swage fitting 78. The swage fitting has an outer thread that engages the inner thread at the end of the wedge bolt. When the fixing nut 80 is fixed to the end of the wedge bolt 60, the guide wire 76 is removed from the end of the wedge bolt 60.

  Although the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the present invention is not limited to the disclosed embodiments, but contrary to the appended claims. It should be understood that it is intended to encompass various modifications and equivalent arrangements included within the spirit and scope.

1 is a perspective view of a downcomer and shroud assembly of a boiling water reactor reactor pressure vessel (RPV). FIG. FIG. 3 is a cross-sectional view of a conventional joint in the upper and lower sections of the downcomer. To illustrate the joint between the upper and lower sections of the downcomer, to the lower part of the two downcomers and the shroud assembly, one downcomer with the slip joint clamp assembly and the other without the clamp assembly It is a perspective view of this pipe fitting. FIG. 6 is a perspective view of a slip joint clamp assembly. FIG. 6 is a cross-sectional view of a transverse pin extending through a slip joint clamp assembly and into a downcomer. FIG. 6 is a perspective view of a clamp wedge for a slip joint clamp assembly. FIG. 6 is a perspective view of a female half housing for a slip joint clamp assembly. FIG. 5 is a perspective view of a partially assembled slip joint clamp assembly attached to a downcomer. FIG. 5 is a perspective view of a partially assembled slip joint clamp assembly attached to a downcomer. FIG. 5 is a perspective view of a partially assembled slip joint clamp assembly attached to a downcomer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Downcomer 12 Boiling water reactor 14 Reactor vessel outer wall 16 Shroud 18 Elbow 20 Pipe line extending through shroud 22 Downcomer slip joint 24 Upper section 26 Lower section 28 Joint sleeve 30 Annular receptacle 32 Slip joint clamp 34 Slip joint upper / lower hole 36 Lateral pin 37 Pin conical tip 38 Male half case 39 Pin head 40 Male connector 42 Female half case 44 Female slot 46 Wedge 48 Wedge wide end 50 Wedge narrow side 52 Wedge-inclined side wall 54 Semi-casing wedge mating groove 56 Wedge side wall in contact with downcomer 58 Wedge bolt hole 60 Wedge bolt 62 Crimp collar 63 Crimp collar half-casing recess 64 Half-casing inner surface Body screw hole 68 Half housing groove 70 Horizontal end of housing 72 End of groove 74 Slot for wedge bolt 76 Guide wire 78 Swage fitting 80 Fixing nut

Claims (10)

A slip joint assembly (32) for a downcomer (10) of a core spray system of a reactor pressure vessel (12) comprising:
A housing sleeve (40, 42) formed around a slip joint (22) in the downcomer where an annular cavity exists between the inner surface of the housing sleeve (40, 42) and the downcomer
An upper wedge (46) and a lower wedge (46) insertable into the cavity;
A wedge that extends through the cavity and extends through the upper and lower wedges and applies a force to pull the upper and lower wedges together to secure the housing sleeve to the downcomer Bolt (60);
An upper pin (36) extending from the housing sleeve into an opening (34) in the upper section of the downcomer pipe;
A slip joint assembly comprising a lower pin (36) extending from the housing sleeve into an opening (34) in a lower section of the downcomer. The slip joint assembly of claim 1, wherein the housing sleeve comprises mating half housings (38, 40), the half housings being joined along an axial end. The upper pin (36) includes an upper lateral pin extending through the upper threaded opening (66) of the housing sleeve into the opening (34) of the upper section of the downcomer, the lower pin (36) including a lateral pin extending through a threaded opening (66) in the lower opening of the housing sleeve into the opening (34) of the lower section of the downcomer. The slip joint assembly according to claim 1. The slip joint of claim 1, wherein the inner surface of the housing sleeve comprises an upper inclined surface (54) for receiving the upper wedge and a lower inclined surface (54) for receiving the lower wedge. assembly. The slip joint assembly of claim 1, further comprising four pairs of the upper wedge (46) and the lower wedge (46), wherein the four pairs are symmetrically disposed about the cavity. A guide wire (76) connected to the end of the wedge bolt (60) during assembly of the slip joint assembly is further provided, wherein the upper wedge slides along the guide wire to the bolt. The slip joint assembly according to claim 1. A slip joint assembly (32) for a downcomer (10) of a core spray system of a reactor pressure vessel (12) comprising:
A housing sleeve (40, 42) formed around a slip joint (22) in the downcomer;
An annular space between the inner surface of the housing sleeve and the downcomer,
An upper wedge (46) and a lower wedge (46) in the cavity and abutting against the inclined surface (54) of the inner surface of the housing sleeve;
A wedge that extends through the cavity and extends through the upper and lower wedges and applies a force to pull the upper and lower wedges together to secure the housing sleeve to the downcomer Bolt (60);
A slip joint assembly comprising a guide wire (76) connected to an end of the wedge bolt during assembly of the slip joint assembly, wherein the upper wedge slides along the guide wire (76) to the bolt. The slip joint assembly of claim 7, wherein the housing sleeve comprises mating half-housings (40, 42) joined along axial ends. An upper lateral pin (36) extending through a threaded opening (66) in the housing sleeve and into an opening (34) in the upper section of the downcomer and a threaded opening (66) in the housing sleeve. The slip joint assembly of claim 7, further comprising a lower transverse pin (36) extending through the opening (34) of the lower section of the downcomer. The said inner surface of the housing sleeve (40, 42) comprises an upper inclined surface (54) for receiving the upper wedge and a lower inclined surface (54) for receiving the lower wedge. Slip joint assembly.

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